Hettiyadura Anusha Priyadarshani Silva, Laskin Alexander
Department of Chemistry, Purdue University, West Lafayette, Indiana, USA.
Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana, USA.
J Mass Spectrom. 2022 Feb;57(2):e4804. doi: 10.1002/jms.4804.
Polycyclic aromatic hydrocarbons (PAHs) are common pollutants present in atmospheric aerosols and other environmental mixtures. They are of particular air quality and human health concerns as many of them are carcinogenic toxins. They also affect absorption of solar radiation by aerosols, therefore contributing to the radiative forcing of climate. For environmental chemistry studies, it is advantageous to quantify PAH components using the same analytical technics that are commonly applied to characterize a broad range of polar analytes present in the same environmental mixtures. Liquid chromatography coupled with photodiode array and high-resolution mass spectrometric detection (LC-PDA-HRMS) is a method of choice for comprehensive characterization of chemical composition and quantification of light absorption properties of individual organic compounds present in the environmental samples. However, quantification of non-polar PAHs by this method is poorly established because of their imperfect ionization in electrospray ionization (ESI) technique. This tutorial article provides a comprehensive evaluation of the quantitative analysis of 16 priority pollutant PAHs in a standard reference material using the LC-MS platform coupled with the ESI source. Results are further corroborated by the quantitation experiments using an atmospheric pressure photoionization (APPI) method, which is more sensitive for the PAH detection. The basic concepts and step-by-step practical guidance for the PAHs quantitative characterization are offered based on the systematic experiments, which include (1) Evaluation effects of different acidification levels by formic acid on the (+)ESI-MS detection of PAHs. (2) Comparison of detection limits in ESI+ versus APPI+ experiments. (3) Investigation of the PAH fragmentation patterns in MS experiments at different collision energies. (4) Calculation of wavelength dependent mass absorption coefficient (MAC) of the standard mixture and its individual PAHs using LC-PDA data. (5) Assessment of the minimal injected mass required for accurate quantification of MAC of the standard mixture and of a multi-component environmental sample.
多环芳烃（PAHs）是大气气溶胶和其他环境混合物中常见的污染物。它们对空气质量和人类健康尤其令人担忧，因为其中许多是致癌毒素。它们还会影响气溶胶对太阳辐射的吸收，从而导致气候的辐射强迫。对于环境化学研究，使用通常用于表征同一环境混合物中存在的多种极性分析物的相同分析技术来量化PAH成分是有利的。液相色谱与光电二极管阵列和高分辨率质谱检测联用（LC-PDA-HRMS）是全面表征环境样品中存在的单个有机化合物的化学成分和量化光吸收特性的首选方法。然而，由于它们在电喷雾电离（ESI）技术中的电离不完全，用这种方法对非极性PAHs进行定量的方法尚不完善。本教程文章对使用与ESI源联用的LC-MS平台对标准参考物质中的16种优先污染物PAHs进行定量分析进行了全面评估。使用对PAH检测更灵敏的大气压光电离（APPI）方法进行的定量实验进一步证实了结果。基于系统实验，提供了PAHs定量表征的基本概念和逐步实践指导，包括：（1）评估甲酸不同酸化水平对PAHs（+）ESI-MS检测的影响。（2）ESI+与APPI+实验中检测限的比较。（3）研究不同碰撞能量下MS实验中PAH的碎裂模式。（4）使用LC-PDA数据计算标准混合物及其单个PAHs的波长依赖性质量吸收系数（MAC）。（5）评估准确量化标准混合物和多组分环境样品的MAC所需的最小进样质量。
